Vacuum cleaning appliances (vacuum cleaners) are used to remove small particles of matter from the environment. Vacuum cleaners typically have an electrically powered fan unit designed to create a high velocity air stream through an inlet nozzle which causes a partial vacuum. The vacuum draws air, dust and other particulate material through the inlet nozzle. The air stream passes through some form of a filter, such as an air permeable bag, whereby material carried by the air stream is trapped on the filter.
As is generally known with regard to many types of appliances, the sale of vacuum cleaners is facilitated by demonstrating their effectiveness. For instance, a salesperson may perform a demonstration wherein a substance, such as sand, is intentionally deposited on a test area to be cleaned (for example, on a potential purchaser's carpet). The vacuum cleaner then is used to remove the substance and provide the potential purchaser with an example of the cleaner's capability. Effectiveness of a vacuum cleaner is demonstrated to a potential customer by 1) permitting the customer to examine the ultimate cleanliness of the test area, and 2) providing the customer with an indication of the amount of material trapped in the filter.
One technique for achieving the latter objective is to disconnect a vacuum bag from an air outlet port on a vacuum cleaner and to install an effluent metering device to the air outlet port. The vacuum then is operated and material drawn into the vacuum nozzle from a test area is discharged into the metering device. Visual inspection of effluent material in the metering device provides a potential purchaser with an indication of the effectiveness of the vacuum cleaner.
One known effluent metering device has an elongated tube which is connectable with the air outlet port on a vacuum cleaner fan unit. A clean test cloth is attached to an open end of the tube to form a bag which encloses the tube end. Such an apparatus for forming a bag with a test cloth is disclosed in Applicant's prior U.S. Pat. No. 4,157,252, issued Jun. 5, 1979. Air discharged by the fan unit passes through the test cloth while effluent material carried in the air stream is trapped on the test cloth. The test cloth is removed from the tube after the fan is deactivated, and a potential purchaser is allowed to inspect the test cloth.
Alternative effluent metering devices also have been proposed. For instance, rather than forming a bag with a test cloth, it is known to attach a preformed mini-bag directly to the end of bag forming tube. Further, enclosed housings having a disposable filter element, such as filter paper, have been used to demonstrate effluent retention in an effluent metering device.
Effluent metering devices of the type discussed above operate effectively only until the buildup of effluent material on the filter element (i.e., a test cloth, a mini-bag, or a filter paper) inhibits the flow of air through the element. Once the filter is clogged and air is prevented from flowing through the element, the metering device is rendered incapable of measuring additional effluent material. Moreover, reduced air flow through an effluent metering device not only limits the amount of material trapped by a filter element (and thus degrades the impact of the filter inspection part of a demonstration), but reduced air flow also decreases the suction power of the fan unit and thereby degrades the capability of a vacuum cleaner to remove a substance from a test area.
Prior effluent metering devices become blocked in an unacceptably short length of time. A need exists for an effluent metering device which provides increased capacity and useful operating life in order to enhance the impact of a vacuum cleaner demonstration.